1. Field of the Invention
The present invention relates generally to the field of display backlight diffusers, and more particularly to an enhanced light diffuser for a liquid crystal display.
2. Description of the Prior Art
Liquid crystal displays have become very popular for use in many products ranging from hand held calculators and watches to communication receivers, due largely to their very low power drive requirements. However, there is a significant drawback when liquid crystal displays are used, in that there must be a source of light, such as sunlight or room light, which is required to illuminate the display to make the displayed information readable. When sunlight or room light is unavailable, such as in the evening, at night, or in a darkened room, the displayed messages become unreadable except with the aid of auxiliary lighting. Such auxiliary lighting has generally been provided by a lamp mounted in front of, adjacent to, or behind the display to provide the light necessary to read the message. When a lamp is provided which is positioned adjacent to the display, the lighting provided has generally been non-uniform, with a "hot", or brightly lit, spot being located on the display near the lamp, and a darkly lit area being located on the display away from the light, both conditions often detracting from the readability of the display. Numerous methods have been employed to overcome the problem of poor light distribution across the display, the most commonly employed being that of using a light diffuser, or wedge in an attempt to provide a more uniform distribution of the auxiliary light across the display to make the message readable in dim lighting situations. The prior art light diffusers have relied on a number of techniques in order to achieve light distribution across a display. One technique which has been employed is the use of a transparent plastic material having a roughened top surface and a reflective back surface, often backed by an opaque reflective tape, the combination of which is intended to improve the distribution of light toward the display. While providing improvement in the light distribution, the "hot" spots have generally remained, as well as a generally non-uniform light distribution across the display. Light wedges, wherein the thickness of the plastic material is reduced across the length of the display, have been used to further enhance the uniformity of the light distribution across the display. Again, while providing improvement in the light distribution, the "hot" spots have generally remained, as well as a noticeable non-uniform light distribution across the display. Other techniques, such as employing multiple auxiliary lamps located at opposite ends of the light wedge, have improved the lighting uniformity, but at a cost of additional power to drive a second auxiliary light source as well as the cost of a second lamp. Still another technique used to provide back lighting for a liquid crystal display, especially a large display has been through the use of a electroluminescent panel which, while providing generally uniform illumination, and which while providing a more uniform illumination, is achieved at a significant cost increase as well as a significant increase in the power required to drive the electroluminescent panel.
What is needed is a light diffuser which utilizes a single light source, and which enhances the distribution of light to more uniformly illuminate a display.